In recent years, semiconductor devices using a compound of III-V group having a greater band gap than Si have been attracting attention. Among these, a semiconductor device using a nitride semiconductor such as gallium nitride (GaN) has characteristics to operate with high speed and low loss. Moreover, a power metal insulator semiconductor field effect transistor (MISFET) using a gallium nitride based nitride semiconductor can perform normally-off operation, and its development is under way.
For example, the undermentioned Patent Document 1 (JP 2014-183125 A) discloses a normally-off type semiconductor device having an electron transit layer formed of i-GaN, an electron supply layer formed of AlGaN, a source electrode, a drain electrode and a gate electrode formed on an insulating film. The gate electrode is formed by lift-off using Ni/Au.